Synergized acetals composition and method for scavenging sulfides and mercaptans

ABSTRACT

This invention provides a composition comprising
         I. at least one reaction product between a nitrogen-free monohydric alcohol and an aldehyde or ketone, and   II. at least one reaction product between a monosaccharide having 3 to 6 carbon atoms and/or an oligosaccharide being formed by oligomerization of monosaccharides having 3 to 6 carbon atoms and an aldehyde or ketone, and optionally   III. at least one reaction product from   III.a) formaldehyde, and   III.b) an amine, selected from the group consisting of primary alkyl amines having 1 to 4 carbon atoms, and primary hydroxy alkyl amines having 2 to 4 carbon atoms, and optionally   IV. at least one solid suppression agent selected from the group consisting of   IV(a). alkali or alkaline earth metal hydroxides   IV(b). mono-, di- or tri-hydroxy alkyl, aryl or alkylaryl amines,   IV(c). mono-, di- or tri-alkyl, aryl or alkylaryl primary, secondary and tertiary amines or   IV(d). multifunctional amines and   IV(e). mixtures of compounds of groups IV(a) to IV(c).   wherein alkyl is C 1  to C 15 , aryl is C 6  to C 15  and alkylaryl is C 7  to C 15 .

The invention relates to a composition and a process for scavenginghydrogen sulfide from liquids and/or gas by using a synergisticcombination of acetals in admixture with a reaction product fromformaldehyde and amines and/or a solids suppression agent. Theformulations containing the inventive composition have particularapplicability in scavenging hydrogen sulfide and/or mercaptans yet atthe same time prevent the formation of unwanted emulsions and/ordeposition of unwanted by-products often associated with usingchemistries and/or formulations of the prior art.

The presence of compounds containing a sulfhydryl group (—SH) andparticularly of hydrogen sulfide pose challenges in many industries.Their presence can create a significant health, safety and environmentalchallenge. There are many different types of compounds containing asulfhydryl group (“sulfhydryl compounds”), with the most commonlyencountered molecules including hydrogen sulfide (H₂S), organo-sulfurcompounds containing R-SH groups (also called mercaptans),thiocarboxylic acids RC(O)SH, dithiocarboxylic acids RC(S)SH, andrelated compounds.

In the oil and gas industry the H₂S content of crude oil and natural gasin many areas of the world is high enough to present environmental andsafety hazards. Hydrogen sulfide is a flammable, corrosive, and highlytoxic gas. H₂S is the most reduced form of sulfur and is produced bysulfate reducing bacteria (SRB) that are often found in anaerobicoilfield environments, or caused by thermal cracking and thermochemicalsulfate reduction (TSR) by hydrocarbons. As crude oil is produced, it isdepressurized and dissolved H₂S is released and can then be transferredto, for example, oil based drilling fluid during the drilling processand this can become a hazard as the drilling fluid is recirculated fromthe well to the surface. During the production phase of crude oil andnatural gas H₂S gas can create a significant asset integrity risk as itis an acid gas and upon dissolving into produced water creates a verycorrosive environment. In addition, the presence of H₂S increases therisks of sulfide stress cracking, hydrogen embrittlement and pittingcorrosion of some structural materials and requires to be removed inorder for fluids and gases to be safely processed.

The odor of sulfhydryl compounds is also a challenge in, for example,metal working environments, but equally in water treatment processes,either municipal (e.g. waste water treatment) or industrial (e.g.recycling of mining water). SRB are often present in the recirculatingfluid systems, and though the bacteria can usually be controlled by theuse of biocidal compositions, often control of the biology in the systemgets lost which results in the development of hazardous H₂S and/ormercaptans in the system. Furthermore biocides are inefficient atremoving H₂S after it forms and only anecdotally scavenge H₂S, viaeither oxidation (e.g. sodium hypochlorite application) or due to therelease of low levels of aldehyde during their breakdown (e.g. withglutaraldehyde). Sulfhydryl compounds and particularly H₂S can presentenvironmental, toxicity and integrity challenges in gaseous phases inconfined spaces, as for instance in sewage treatment facilities andparticularly in shipping and storage containers for moisture sensitivematerials that may emit H₂S which can accumulate in the gaseousheadspace. It would be desirable to have a scavenger that can reduce theH₂S concentration in such locations.

Most commonly used sulfhydryl scavengers are based on metals as forexample copper, zinc or iron which are converted to insoluble sulfides.A number of alternative, metal free methods have been proposed toscavenge hydrogen sulfide and to control sulfhydryl odors in hydrocarboncontaining systems, including:

WO-98/02501 describes the use of bisoxazolidines prepared by thereaction of 1,2- or 1,3-amino alcohols containing 3 to 7 carbon atomswith aldehydes containing 4 or fewer carbon atoms, as for example3,3′-methylenebis-5-methyloxazolidine. The relative oil and watersolubility of these products can be controlled through the choice ofstarting materials. These bisoxazolidines react with sulfhydrylcompounds present in oil and gas streams to neutralize and thereforescavenge them.

U.S. Pat. No.-5,347,004 teaches the use of reaction products ofalkoxyalkylene amine, optionally in admixture with ammonia and/oralkylamines with aldehydes to remove H₂S from gas streams which aresparged into water solutions of the reaction products.

WO-2014/031537 teaches the use of an aldehyde releasing compound,preferably a hydantoin compound, to remove sulfhydryl compounds fromhydrocarbon fluids.

U.S. Pat. No.-3,928,211 describes the use of inorganic zinc salts (mostpreferably zinc carbonate) preferably dispersed in aqueous ornon-aqueous oil well drilling fluids with an organic dispersant such aslignin containing materials for scavenging hydrogen sulfide in aqueousdrilling fluids.

WO-2002/051968 teaches a process for reducing the level of hydrogensulfide in a liquid or gas by treatment of the liquid or gas with anH₂S-scavenger product derivable from the reaction of a carbonylgroup-containing compound with an alcohol, thiol, amide, thioamide, ureaor thiourea. The carbonyl group-containing compound is preferablyformaldehyde, and preferably the product is derivable by reaction offormaldehyde with an amine-free alcohol or urea selected from ethyleneglycol, propylene glycol, glycerol, diethylene glycol, triethyleneglycol, ethyl alcohol, n-butanol, a sugar, a low molecular weightpolyvinyl alcohol, castor oil fatty acid and urea. More especially, thescavenger product is used with an amine, especially monoethanolamine ormonoethanolamine triazine.

U.S. Pat. No.-4,978,512 teaches a method of reducing H₂S levels, themethod comprising bringing the H₂S containing medium into contact withinter alia acetals and bisoxazolidines.

The object of this invention is to provide compositions which can beused for scavenging of sulfhydryl compounds in crude oil, gasproduction, water production, water injection and combinations thereof,preferably, but not limited to H₂S and/or mercaptans. The compositionsof the invention should be notable for improved safety and performancecompared to the formulations and chemistries of the prior art, i.e. theyshould contain low amounts of toxic substances like free formaldehydeeven after prolonged storage. They should have a higher scavengingefficiency than scavengers according to the state of the art andespecially for the treatment of gases as for example of natural gas theyshould assure an efficient scavenging of sulfhydryl compounds within ashort contact time. Furthermore it is desirable to have a scavenger thatdoes not produce unwanted solid by-products and/or form emulsions thatcan inadvertently contaminate the very systems they are treating. Inparticular the formation of solid products which may plug lines andvessels shall be retarded or even inhibited in order to facilitate theremoval of the sulfhydryl reaction products formed during the scavengingprocess.

Surprisingly it has been found that a composition comprising at leastone reaction product between a monohydric alcohol and an aldehyde orketone and at least one reaction product of a monosaccharide having 3 to6 carbon atoms and/or an oligosaccharide being formed by oligomerizationof monosaccharides having 3 to 6 carbon atoms with an aldehyde havingone or two carbon atoms shows improved capability in scavengingsulfhydryl compounds in comparison to the respective reaction productsof the individual alcohols. Such composition allows i) for a lowerdosage rate of scavenger to obtain the same level of residual amount ofsulfhydryl compound and/or ii) for a lower level of residual amount ofsulfhydryl compound with the same dosage rate of scavenger. Furthermore,in combination with at least one reaction product from formaldehyde andan amine (hereinafter also referred to as “synergist”) the kinetics ofscavenging H₂S and/or mercaptans provided by the reaction products of amonohydric alcohol with an aldehyde or ketone and a monosaccharidehaving 3 to 6 carbon atoms and/or an oligosaccharide being formed byoligomerization of monosaccharides having 3 to 6 carbon atoms with analdehyde having one or two carbon atoms can be significantlyaccelerated. Alternatively to the synergist or in addition to thesynergist, the admixture of a solids suppression agent as a furthersynergistic additive facilitates the removal of sulfhydryl reactionproducts especially in continuously operated scavenging processes.Furthermore the admixture of the synergist and/or the further synergistextends the gas breakthrough time of sulfhydryl compounds in a contacttower containing the reaction products of a monohydric alcohol with analdehyde and/or ketone and a monosaccharide having 3 to 6 carbon atomsand/or an oligosaccharide being formed by oligomerization ofmonosaccharides having 3 to 6 carbon atoms with an aldehyde having oneor two carbon atoms.

The use of the synergist and/or the further synergist of the inventionenables the mixed hemiacetals and acetals to react much more efficientlywith sulfhydryl compounds and especially with H₂S. The mechanismbelieved to be involved in this reaction, but which should not beconsidered to be limiting to the invention in any way, occurs due to thelikelihood that the synergist component reacts preferentially with H₂Sforming an intermediate reaction complex which then in turn reacts witha molecule of hemiacetal respectively acetal reforming a molecule ofsynergist and liberation of the corresponding alcohol present in the(hemi-)acetal. After the H₂S scavenging process the residual synergistthen works as a corrosion inhibitor, protecting the integrity of thepipelines and equipment in which it has been applied.

Within the scope of this application the expressions “hemiacetal” and“acetal” encompass the reaction products of an alcohol with either analdehyde or a ketone, i. e. they include hemiketals respectively ketalswhen using a ketone instead of an aldehyde in the reaction with anmonohydric alcohol. The expression “(hemi-)acetals” encompasseshemiacetals, acetals and their mixtures which are often formed duringreaction of alcohols and carbonyl compounds.

In a first aspect of the invention, there is provided a compositioncomprising

-   -   I. at least one reaction product between a nitrogen-free        monohydric alcohol and an aldehyde or ketone, and    -   II. at least one reaction product between a monosaccharide        having 3 to 6 carbon atoms and/or an oligosaccharide being        formed by oligomerization of monosaccharides having 3 to 6        carbon atoms with an aldehyde having one or two carbon atoms.

In a second aspect of the invention there is provided a compositioncomprising

-   -   I. at least one reaction product between a nitrogen-free        monohydric alcohol and an aldehyde or ketone, and    -   II. at least one reaction product between a monosaccharide        having 3 to 6 carbon atoms and/or an oligosaccharide being        formed by oligomerization of monosaccharides having 3 to 6        carbon atoms with an aldehyde having one or two carbon atoms,        and    -   III. at least one reaction product from formaldehyde and ammonia        and/or an amine selected from the group consisting of primary        alkyl amines having 1 to 10 carbon atoms and primary hydroxy        alkyl amines having 2 to 10 carbon atoms.

In a third aspect of the invention there is provided a compositioncomprising

-   -   I. at least one reaction product between a nitrogen-free        monohydric alcohol and an aldehyde or ketone, and    -   II. at least one reaction product between a monosaccharide        having 3 to 6 carbon atoms and/or an oligosaccharide being        formed by oligomerization of monosaccharides having 3 to 6        carbon atoms with an aldehyde or ketone, and    -   IV. at least one inorganic or organic alkaline compound that        functions as a solids suppression agent.

In a fourth aspect of the invention there is provided a compositioncomprising

-   -   I. at least one reaction product between a nitrogen-free        monohydric alcohol and an aldehyde or ketone, and    -   II. at least one reaction product between a monosaccharide        having 3 to 6 carbon atoms and/or an oligosaccharide being        formed by oligomerization of monosaccharides having 3 to 6        carbon atoms with an aldehyde having one or two carbon atoms,        and    -   III. at least one reaction product from formaldehyde and ammonia        and/or an amine selected from the group consisting of primary        alkyl amines having 1 to 10 carbon atoms and primary hydroxy        alkyl amines having 2 to 10 carbon atoms, and    -   IV. at least one inorganic or organic alkaline compound that        functions as a solids suppression agent.

In a fifth aspect of the invention, there is provided the use of thecomposition of the first, second, third or fourth aspect of theinvention as a scavenger for sulfhydryl compounds for application inoilfield operations and process systems.

In a sixth aspect of the invention, there is provided a process forscavenging sulfhydryl compounds in oilfield operations and processsystems, the process comprising adding to a system susceptible toliberation of sulfhydryl compounds the composition of the first, second,third or fourth aspect of the invention.

In a seventh aspect of the invention there is provided the use of atleast one reaction product from

-   -   III. formaldehyde and ammonia and/or an amine, selected from the        group consisting of primary alkyl amines having 1 to 10 carbon        atoms and primary hydroxy alkyl amines having 2 to 10 carbon        atoms,

as a synergist in the reaction between

-   -   a) I. the reaction product between a nitrogen-free monohydric        alcohol and an aldehyde or ketone, and    -   a) II. the reaction product between a monosaccharide having 3 to        6 carbon atoms and/or an oligosaccharide being formed by        oligomerization of monosaccharides having 3 to 6 carbon atoms        with an aldehyde having one or two carbon atoms, and    -   b) a sulfhydryl compound.

In an eighth aspect of the invention there is provided the use of atleast

-   -   IV. one inorganic or organic alkaline compound

as a solids suppression agent in the reaction between

-   -   a) I. the reaction product between a nitrogen-free monohydric        alcohol and an aldehyde or ketone, and    -   a) II. the reaction product between a monosaccharide having 3 to        6 carbon atoms and/or an oligosaccharide being formed by        oligomerization of monosaccharides having 3 to 6 carbon atoms        with an aldehyde or ketone, and    -   b) a sulfhydryl compound.

In preferred embodiments of the invention, at least one demulsifier (V)and/or corrosion inhibitor (VI) is present in any aspect of theinvention.

Group I

The group I compound is the reaction product of a monohydric alcohol andan aldehyde or ketone. The monohydric alcohol does not contain nitrogen.

Preferred monohydric alcohols as starting materials are alkyl, aryl andarylalkyl alcohols containing one hydroxy group and 1 to 15 carbonatoms, more preferably 1 to 10 carbon atoms and especially 2 to 5 carbonatoms as for example 1 to 5, or 2 to 15 or 2 to 10 carbon atoms. Thehydroxyl group of preferred monohydric alcohols is bound to analiphatic, alicyclic and/or aromatic moiety, preferably to an aliphatic,alicyclic and/or aromatic hydrocarbon moiety, and more especially to analiphatic or cycloaliphatic hydrocarbon moiety. The aliphatic andcycloaliphatic moieties may be saturated or unsaturated, preferably theyare saturated. Aliphatic moieties with 3 or more carbon atoms may belinear or branched. More especially the monohydric alcohol is aliphatic.In particular the alcohol is an alkyl alcohol. Examples for preferredalcohols are methanol, ethanol, propanol, iso-propanol, n-butanol,iso-butanol, tert-butanol and the various isomers of pentanol, hexanol,heptanol and methanol and ethanol.

Preferred aldehydes or ketones as starting materials contain one or morecarbonyl groups, more preferably one or two carbonyl groups andespecially one carbonyl group. Furthermore, preferred aldehydes andketones contain 1 to 10 carbon atoms, more preferably 1 to 7, andespecially 1 to 4 carbon atoms. In preferred aldehydes the carbonylgroup carries one and in preferred ketones two aliphatic, alicyclicand/or aromatic substituents. More preferably the substituents arealiphatic, alicyclic and/or aromatic hydrocarbon substituents andespecially preferred the substituents are aliphatic hydrocarbon groups.Preferred aliphatic and cycloaliphatic substituents may be saturated orunsaturated, most preferably they are saturated. In a particularlypreferred embodiment the saturated aliphatic groups are alkyl groups. Inketones both substituents may be the same or different.

In a preferred embodiment the carbonyl compound is an aldehyde, morepreferably a mono- or di-aldehyde, and especially formaldehyde. Itshould be understood that the terms “aldehyde” and “formaldehyde”include precursors like e.g. para-formaldehyde, formalin, and otherchemical forms from which the basic structure HCHO can be released orset free during the reaction with an alcohol. Other suitable aldehydesinclude, for example, acetaldehyde, propionaldehyde, butyraldehyde,glutaraldehyde and glyoxal. Suitable ketones include, for example,acetone, methyl ethyl ketone, diethylketone, methyl isopropyl ketone,hexanones and heptanones.

Mixtures of two or more carbonyl compounds, for example two or more ofthe aldehydes mentioned above, e.g. formaldehyde and one or more otheraldehydes, may be used if desired.

In the reaction between monohydric alcohol and aldehyde and/or ketonepart or all of the alcohols may be converted to hemiacetals and/oracetals. In a preferred embodiment, the reaction product is ahemiacetal. In a preferred embodiment at least 50 mol- % of the alcohol,more preferably 60 to 99 mol- % of the alcohol, especially 65 to 95 mol-% of the alcohol and especially preferred 70 to 90 mol- % of the alcoholas for example more than 60 mol- %, more than 65 mol- %, more than 70mol- %, % of the alcohol or 50 to 99 mol- %, 50 to 95 mol- %, 50 to 90mol- %, 60 to 95%, 60 to 90 mol- %, 65 to 99 mol- %, 65 to 90 mol- %, 70to 99 mol- % or 70 to 95 mol- % of the alcohol are converted tohemiacetals and/or acetals. In case the degree of conversion is low someunreacted monohydric alcohol remains in the composition. The presence ofresidual alcohol in the reaction mixture has proven to be advantageousas upon its reaction with sulfhydryl compounds often the formation ofsolid precipitate gets reduced. Furthermore, remaining alcohol will actas a solvent.

Group II

The group II compound is the reaction product of a monosaccharide having3 to 6 carbon atoms or an oligosaccharide being formed byoligomerization of monosaccharides having 3 to 6 carbon atoms with analdehyde having one or two carbon atoms. The monosaccharide having 3 to6 carbon atoms respectively the oligosaccharide being formed byoligomerization of monosaccharides having 3 to 6 carbon atoms and thealdehyde having one or two carbon atoms are different. In a preferredembodiment the group II compound is the reaction product of amonosaccharide having 3 to 6 carbon atoms with an aldehyde having one ortwo carbon atoms. In a further preferred embodiment the group IIcompound is the reaction product of an oligosaccharide being formed byoligomerization of monosaccharides having 3 to 6 carbon atoms with analdehyde having one or two carbon atoms.

In a preferred embodiment the monosaccharide having 3 to 6 carbon atomsis a polyhydroxyaldehyde (aldose). In a further preferred embodiment themonosaccharide having 3 to 6 carbon atoms is a polyhydroxyketone(ketose). In a further preferred embodiment the monosaccharide having 3to 6 carbon atoms is a mixture of a polyhydroxyaldehyde with apolyhydroxyketone.

Monosaccharides as starting materials for the group II compounds have 3to 6, preferably 4 to 6 and especially 5 or 6 carbon atoms. Besides thecarbonyl group they carry at least 2, preferably 3 to 5 and especiallypreferred 4 or 5 hydroxyl groups. In preferred embodiments all carbonatoms except the carbonyl carbon carry a hydroxyl group. Where differentstereoisomers or enantiomers of the polyhydroxyaldehyde respectively thepolyhydroxyketone exist all of them are equally suited. However, in apreferred embodiment, the polyhydroxyaldehyde respectively thepolyhydroxyketone, except dihydroxyacetone, is the D-enantiomer.

Preferred polyhydroxyaldehydes and -ketones have the general formula (1)

C_(n)(H₂O)_(n)   (1)

wherein n is an integer between 3 and 6 and preferably between 4 and 6as especially preferred 5 or 6.

Preferred polyhydroxyaldehydes have the general formula (2). Preferredpolyhydroxyketones have the general formula (3)

CHO—(CH—OH)_(m)—CH₂OH   (2)

HO—CH₂—C(═O)—(CH—OH)_(p)—CH₂OH   (3)

wherein m is 1,2,3 or 4 and p is 0, 1, 2 or 3.

In a preferred embodiment the polyhydroxyaldehyde according to formulae1 and 2 is glyceraldehyde (n=3; m=1).

In a further preferred embodiment the polyhydroxyketone according toformulae 1 and 3 is dihydroxyacetone (n=3; p=0)

In a further preferred embodiment the polyhydroxyaldehyde according toformulae 1 and 2 is selected from the group consisting of erythrose andthreose (n=4; m=2).

In a further preferred embodiment the polyhydroxyketone according toformulae 1 and 3 is erythrulose (n=4; p=1)

In a further preferred embodiment in the polyhydroxyaldehyde accordingto formulae 1 and 2, n is 5 and m is 3. Examples for preferredpolyhydroxyaldehydes are ribose, arabinose, xylose and lyxose.

In a further preferred embodiment in the polyhydroxyketone according toformulae 1 and 3, n is 5 and p is 2. Examples for preferredpolyhydroxyketones are ribulose and xylulose.

In a further preferred embodiment in the polyhydroxyaldehyde accordingto formulae 1 and 2 n is 6 and m is 4. Examples for preferredpolyhydroxyaldehydes are allose, altrose, glucose, mannose, gulose,idose, galactose and talose.

In a further preferred embodiment in the polyhydroxyketone according toformulae 1 and 3 n is 6 and p is 3. Examples for preferredpolyhydroxyketones are psicose, fructose, sorbose and tagatose.

Examples for preferred polyhydroxyaldehydes are the following aldoses:

Examples for preferred polyhydroxyketones are the following ketoses:

In a preferred embodiment the polyhydroxyaldehydes and/orpolyhydroxyketones are in open chain form as depicted above.

In a further preferred embodiment the polyhydroxyaldehydes and/orpolyhydroxyketones with 5 and 6 carbon atoms are in a cyclic hemiacetalrespectively hemiketal form. Ring closure by condensation corresponds toreaction between the carbonyl group and either the C-4-OH or C-5-OH inthe open chain polyhydroxyaldehydes respectively polyhydroxyketones.Cyclization involving O-4 results in a five-membered ring structurallyrelated to furan and therefore designated as a furanose, whilsthemiacetal formation with O-5 gives rise to an essentially strain-free,hence sterically more favored, six-membered ring, a derivative of pyran,hence termed a pyranose. Most often, especially in aqueous solution,open chain form and cyclic form are in equilibrium. In a preferredembodiment the polyhydroxyaldehyde and/or polyhydroxyketone to bereacted with the aldehyde having one or two carbon atoms is a mixture ofopen chain and cyclic forms.

Suited cyclic structures are exemplified for glucose and fructose informulae groups 4 and 5. The same principle is applicable for allpolyhydroxyaldehydes and polyhydroxyketones where n stands for 5 or 6.

In a preferred embodiment the polyhydroxyaldehyde and/orpolyhydroxyketone as starting material for the group II compound maycomprise further functionalities other than a carbonyl group andhydroxyl groups, including but not limited to amino groups or carboxylicacid groups. Examples for suitable amino derivatives are aldoses whichhave a hydroxyl group replaced by an amino functionality as for examplein D-glucosamin (2-amino-2-deoxy-D-glucose). The amino group mayfurthermore be acylated with a carboxylic acid having 1 to 18 carbonatoms as for example with acetic acid. Examples for suited derivativescontaining a carboxylic acid group are uronic acids which contain acarboxylic acid substituting the chain terminating hydroxymethyl group,as for example D-glucuronic acid. Likewise the carboxylic acid groupsmay be in the form of their alkali, earth alkaline, ammonium or alkylammonium salt. In preferred alkyl ammonium salts the nitrogen atomcarries 1, 2, 3 or 4 alkyl residues with independently 1 to 6 carbonatoms each, and optionally a hydroxyl group in the alkyl residue. In apreferred embodiment the polyhydroxyaldehyde and/or polyhydroxyketonedoes not contain nitrogen. In a further preferred embodiment thepolyhydroxyaldehyde and/or polyhydroxyketone does not contain acarboxylic acid group nor its derivative.

The most preferred polyhydroxyaldehydes used as starting material forthe group II compound are glucose, mannose, galactose, ribose, arabinoseand xylose. The most preferred polyhydroxyketone used as startingmaterials for the group II compound is fructose.

Preferred oligosaccharides as starting materials for the group IIcompounds are oligomers formed by oligomerization of above describedaldoses and/or ketoses having 3 to 6 carbon atoms and being joined by aglycosidic linkage. Especially preferred aldoses and ketoses asmonomeric units are those having 4 to 6 carbon atoms and especiallythose having 5 or 6 carbon atoms. More preferred oligomers contain twoto five and especially two or three monosaccharide units each joined byglycosidic linkages.

In a more preferred embodiment the oligosaccharides as startingmaterials for the group II compounds contain two monosaccharide units.Each unit has 3 to 6 carbon atoms, more preferred 4 to 6 carbon atomsand especially preferred 5 or 6 carbon atoms. The units are joined by aglycosidic linkage. Usually the glycosidic linkage is formed between thehydroxyl group resulting from hemiacetalisation of a firstmonosaccharide and subsequent acetalisation with a hydroxyl group of afurther monosaccharide.

In a preferred embodiment the oligosaccharide being formed byoligomerization of monosaccharides having 3 to 6 carbon atoms isnon-reducing, i.e. all the carbonyl groups are converted to acetalgroups. In a further preferred embodiment the oligosaccharide beingformed by oligomerization of monosaccharides having 3 to 6 carbon atomsis reducing, i.e. the oligosaccharide contains a hemiacetal group. Thelatter is in equilibrium with the open chain form and allows the sugarto act as a reducing agent, for example in the Fehling's test, Tollens'test or Benedict's test.

In a further preferred embodiment the oligosaccharide is ahomo-oligosaccharide being formed from only one type of monosaccharide.Examples for homo-disaccharides are maltose, Isomaltose, cellobiose andtrehalose. In a further preferred embodiment the oligosaccharide is ahetero-oligosaccharide being formed from at least two differentmonosaccharides each having 3 to 6 carbon atoms, more preferred 4 to 6carbon atoms and especially preferred 5 or 6 carbon atoms.

Examples for hetero-disaccharides are sucrose, isomaltulose, andtrehalulose, each being composed of glucose and fructose as well aslactose (glucose and galactose) and lactulose (fructose and galactose).An example for a trisaccharide is raffinose.

In a preferred embodiment the disaccharide has the general formula (6)

C_(y)(H₂O)_(y-1)   (6)

wherein y is an integer between 10 and 12. Especially preferred y is 12.

Most preferred oligosaccharides formed by oligomerization ofmonosaccharides having 3 to 6 carbon atoms as starting materials for thegroup II compounds are sucrose, lactose, cellobiose and maltose.

The majority of monosaccharides having 3 to 6 carbon atoms and ofoligosaccharides formed by oligomerization of monosaccharides having 3to 6 carbon atoms occur naturally in the vegetable kingdom. Accordinglythey can be extracted from plant raw material or marine algae. Othersare accessible by chemical or enzymatic hydrolysis of higherpolysaccharides as for example from starch or cellulose.

For the reaction between a monosaccharide having 3 to 6 carbon atomsand/or an oligosaccharide formed by oligomerization of monosaccharideshaving 3 to 6 carbon atoms with and aldehyde and/or ketone themonosaccharide having 3 to 6 carbon atoms and/or the oligosaccharideformed by oligomerization of monosaccharides having 3 to 6 carbon atomsmay be applied as a solid or as a concentrated solution often calledsyrup.

Preferred aldehydes as starting materials for the group II compounds areformaldehyde, acetaldehyde and glyoxal. Most preferred aldehyde asstarting material for group II compounds is formaldehyde. It should beunderstood that the terms “aldehyde” and “formaldehyde” includeprecursors like e.g. para-formaldehyde, formalin, and other chemicalforms from which the basic structure HCHO can be released or set freeduring the reaction with an alcohol. The aldehyde used for reaction withthe monosaccharide having 3 to 6 carbon atoms and/or the oligosaccharideformed by oligomerization of monosaccharides having 3 to 6 carbon atomsmay be the same as the one used for the monohydric alcohol, or it may bea different one.

In the reaction between a monosaccharide having 3 to 6 carbon atomsand/or the oligosaccharide being formed by oligomerization ofmonosaccharides having 3 to 6 carbon atoms with and aldehyde part or allof the free hydroxyl groups may be converted to hemiacetals. In apreferred embodiment at least 50 mol- % of the hydroxyl groups, morepreferably 60 to 99 mol- % of the hydroxyl groups, especially 65 to 95mol- % of the hydroxyl groups and especially preferred 70 to 90 mol- %of the hydroxyl groups as for example more than 60 mol- %, more than 65mol- %, more than 70 mol- %, or 50 to 99 mol- %, 50 to 95 mol- %, 50 to90 mol- %, 60 to 95%, 60 to 90 mol- %, 65 to 99 mol- %, 65 to 90 mol- %,70 to 99 mol- % or 70 to 95 mol- % of the hydroxyl groups are convertedto hemiacetals. In case the degree of conversion is low some unreactedhydroxyl groups of the monosaccharide having 3 to 6 carbon atoms and/orthe oligosaccharide formed by oligomerization of monosaccharides having3 to 6 carbon atoms remain in the composition. The presence of residualhydroxyl groups in the reaction mixture has proven to be advantageous asupon its reaction with sulfhydryl compounds the formation of solidprecipitate gets reduced.

In a particularly preferred embodiment the reaction product between themonosaccharide having 3 to 6 carbon atoms and/or the oligosacchariderespectively the monohydric alcohol and the aldehyde is predominantly amixture of hemiacetals and acetals. Preferred are reaction productswherein the ratio between hemiacetals and acetals on a molar basis isbetween 100:1 and 1:10 more preferably between 50:1 and 1:5 andespecially between 20:1 and 1:1 as for example between 100:1 and 1:5 orbetween 100:1 and 1:1 or between 50:1 and 1:10 or between 50:1 and 1:1or between 20:1 and 1:10 or between 20:1 and 1:5.

Reactions of aldehydes and ketones with alcohols are described in theliterature. “Formaldehyde”, p 265, Joseph Frederic Walker, reprint 1975,Robert E. Krieger Publishing Company Inc. discloses that hemiacetals areobtained when formaldehyde and alcohols are brought together underneutral or alkaline conditions, and that they form readily in the caseof primary and secondary alcohols.

The synthesis of compounds of group I and group II may be accomplishedin separate reactions. Preferably it is accomplished in a simultaneousreaction using a one pot reaction by charging a mixture of monohydricalcohol and monosaccharide having 3 to 6 carbon atoms and/oroligosaccharide formed by oligomerization of monosaccharides having 3 to6 carbon atoms and reacting this mixture with an aldehyde having one ortwo carbon atoms. A one-pot reaction is especially preferred when thealdehyde used for the reaction with the monohydric alcohol is the sameas the aldehyde used for the reaction with the monosaccharide having 3to 6 carbon atoms and/or the oligosaccharide formed by oligomerizationof monosaccharides having 3 to 6 carbon atoms.

For ease of reaction the presence of an aqueous solvent has proven to beadvantageous. Preferably the reaction is made in the presence of 5 to 70wt.- %, more preferably in the presence of 10 to 50 wt.- % andespecially in the presence of 15 to 40 wt.- % of water in respect to theoverall reaction mass. Often the amount of water introduced by thereactants like for example by formalin is sufficient. In a preferredembodiment the water remains in the reaction product.

In the synthesis of compounds of group I and group II the molar ratio ofhydroxyl groups in the monohydric alcohol respectively themonosaccharide having 3 to 6 carbon atoms and/or the oligosaccharideformed by oligomerization of monosaccharides having 3 to 6 carbon atomsto carbonyl groups of the aldehyde is preferably between 20:1 and 1:5and more preferably between 10:1 and 1:2 and especially between 2:1 and1:1 as for example between 20:1 and 1:2 or between 20:1 and 1:1 orbetween 10:1 and 1:5 or between 10:1 and 1:1 or between 2:1 and 1:5 orbetween 2:1 and 1:2. In a preferred embodiment the reactants are reactedin a substantially stoichiometric ratio.

However, in order to reduce the presence of residual free (unreacted)aldehyde in the final product to extremely low levels it has proven tobe advantageous not to proceed to full reaction of all hydroxyl groups,i.e. to react only part of the hydroxyl groups of the alcohol of group Iand/or of the monosaccharide having 3 to 6 carbon atoms and/or theoligosaccharide formed by oligomerization of monosaccharides having 3 to6 carbon atoms of group II with the aldehyde. Accordingly, in apreferred embodiment the reaction between the monohydric alcohol and thealdehyde is made with less than the stoichiometric amount of aldehydecompound in respect to the hydroxyl groups of the alcohol. In a furtherpreferred embodiment the reaction between the monosaccharide having 3 to6 carbon atoms and/or the oligosaccharide formed by oligomerization ofmonosaccharides having 3 to 6 carbon atoms and the aldehyde having oneor two carbon atoms is made with less than the stoichiometric amount ofaldehyde compound in respect to the hydroxyl groups of themonosaccharide having 3 to 6 carbon atoms and/or the oligosaccharideformed by oligomerization of monosaccharides having 3 to 6 carbon atoms.A preferred molar ratio of aldehyde groups to hydroxyl groups is between1.01:1.50 and especially between 1.05 and 1.20 as for example between1.01 and 1.20 or between 1.05 and 1.50. The ratios given above similarlyapply for the reaction of the aldehyde compound with the monohydricalcohol of group I respectively with the monosaccharide having 3 to 6carbon atoms and/or the oligosaccharide being formed by oligomerizationof monosaccharides having 3 to 6 carbon atoms of group II in separatereaction steps as well as for the reaction with their mixture in aone-pot reaction. For separate reactions part or all of the aldehydeused for the reaction with the monohydric alcohol can be substituted bya ketone.

Group III

The group III component is optional. The group III compound is thereaction product from formaldehyde with ammonia and/or an amine, theamine being selected from the group consisting of primary alkyl amineshaving 1 to 10 carbon atoms and primary hydroxy alkyl amines having 2 to10 carbon atoms. This group comprises the synergist component of theinventive composition according to the second and fourth aspect of theinvention.

Preferred primary amines comprise 1 to 4 carbon atoms, preferred primaryhydroxy amines 2 to 4 carbon atoms. Especially preferred primary hydroxyamines correspond to the formula (7)

HO—A—NH₂   (7)

wherein A is a linear or branched alkylene group with 2 to 4 carbonatoms.

Examples of nitrogen containing compounds suitable for the presentinvention include, but are not limited to: ammonia, methylamine,ethylamine, propylamine, isopropyl amine, monoethanolamine,1-amino-2-propanol, 3-amino-1-propanol, 2-amino-1-butanol,3-amino-1-butanol, 3-amino-1-butanol, 2-ethoxypropylamine,3-ethoxypropylamine, 1-methoxyisopropylamine and 2-methoxyethylamine.

The nitrogen containing compound and formaldehyde may be reacted in anymolar ratio with a preferred ratio being from 1 mole aldehyde to 10moles nitrogen containing compound to 10 moles aldehyde to 1 molenitrogen containing compound, a more preferred ratio being from 1 molealdehyde to 5 moles nitrogen containing compound to 5 moles aldehyde to1 mole nitrogen containing compound, an even more preferred ratio being1 mole aldehyde to 3 moles nitrogen containing compound to 3 molesaldehyde to 1 mole nitrogen containing compound and a most preferredratio being 1 mole aldehyde to 1 mole nitrogen containing compound.

The structure of the aminal formed from the reaction of formaldehyde andthe nitrogen containing compound is dependent upon the selected nitrogencontaining compound and the selected molar ratio between formaldehydeand nitrogen compound, as is self-evident to those of ordinary skill inthe art. Similarly, mixtures of the above nitrogen containing compoundsmay also be reacted in order to form singular, or mixtures of variousaminals as is also evident to one of ordinary skill in the art.

In one preferred embodiment the reaction product corresponds to formula(7a)

wherein

R is H or methyl, and

n is 1 or 2.

In an especially preferred embodiment R is CH₃. In another especiallypreferred embodiment, n is 1. In a particularly preferred embodiment nis 1 and R is CH₃. The name of this compound is3,3′-methylenebis-5-methyl-oxazolidine (MBO).

In another preferred embodiment the reaction product corresponds toformula (7b)

wherein each R² is C₁ to C₄ alkyl or C₂ to C₄ hydroxy alkyl. Examplesfor especially preferred compounds arehexahydro-1,3,5-trimethyl-s-triazine,hexahydro-1,3,5-triethyl-s-triazine,hexahydro-1,3,5-tris(hydroxymethyl)-s-triazine andhexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine.

Mixtures of different reaction products of structures 7a and 7b areequally suited. The substituents R and R² may be the same or different.

Group IV

The group IV component is optional. The group IV compound is aninorganic or organic alkaline compound. This group comprises the solidssuppression agent of the inventive composition according to the thirdand fourth aspect of the invention.

The solid usually formed by the reaction of group I and group IIcompounds with hydrogen sulfide is 1,3,5-trithiane. Addition of analkaline compound to the compounds of groups I and II prevents or atleast retards the formation of the poorly soluble 1,3,5-trithiane upontheir reaction with sulfhydryl compounds. Without being bound to thistheory it is believed that different intermediates as for examplepolyoxymethylenesulfide oligomers are formed and stabilized by thepresence of the alkaline compound of group IV. By preventing theformation of solids the scavenging composition remains homogeneous andespecially in a contact tower application allows for more efficient andup to quantitative use of the (hemi-)acetals of group I and II compoundsand thereby reduces the amount of chemicals required. This may result inan extended gas breakthrough time in such scavenging applications.Additionally, in direct injection applications for continuous scavengingof sulfhydryl compounds from e.g. natural gas streams the removal of theliquid reaction products is much easier than removal of solids and it isnot prone to blockage of tubings and vessels.

Furthermore, in the presence of an alkaline compound of group IV thestability of compounds I and II is increased and e.g. gassing offormaldehyde is further reduced or even prevented. This leads to afurther reduced level of free formaldehyde in the space above thecomposition and thereby further improves the safety of the personnelhandling the inventive composition.

Preferably, the compound of group IV is soluble in, or miscible with themixture of compounds of groups I and II. In a further preferredembodiment the compound of group IV is soluble in, or miscible with theformulation of the mixture of compounds of groups I and II in thepresence of an aqueous solvent.

In a preferred embodiment, the alkaline compound is selected from thegroup consisting of

IV(a). alkaline metal salts or alkaline earth metal salts,

IV(b). ammonia; alkyl amines, aryl amines or alkylaryl amines,

IV(c). hydroxy alkyl amines, hydroxy aryl amines or hydroxy alkylarylamines,

IV(d). multifunctional amines, and

IV(e). mixtures of compounds of groups IV(a) to IV(c).

In an aryl amine, the N atom is bonded to the aromatic system. In analkyl aryl amine, the N atom may be bonded to either the aromatic systemor the alkyl group.

Preferred cations of the alkaline metal and alkaline earth metal saltsIV(a) are derived from lithium, sodium, potassium, rubidium, beryllium,magnesium, calcium and strontium with sodium, potassium and calciumbeing especially preferred. Preferred anions are hydroxyl and carbonategroups with hydroxyl being especially preferred.

Examples for preferred alkali or alkaline earth metal salts LiOH, NaOH,KOH, Mg(OH)₂, Ca(OH)₂, Be(OH)₂, Na₂CO₃, K₂CO₃, NaHCO₃, KHCO₃, BeCO₃,MgCO₃, CaCO₃, Mg(HCO₃)₂, Ca(HCO₃)₂ and their mixtures. Especiallypreferred alkali and alkaline earth metal salts of group IVa are NaOH,KOH, Mg(OH)₂ and Ca(OH)₂.

The amines of group IV(b) may be primary, secondary or tertiary amines.Preferred amines have up to 20 carbon atoms, more preferably between 1and 10 and especially between 2 and 4 carbon atoms as for examplebetween 1 and 20, between 1 and 4, between 2 and 20 or between 2 and 10carbon atoms. Preferred hydrocarbyl residues are alkyl, aryl andalkylaryl residues, with alkyl residues being particularly preferred. Insecondary and tertiary amines the hydrocarbyl residues may be the sameor different. Especially preferred amines are alkyl amines with 1 to 4carbon atoms per alkyl residue. Examples for especially preferred aminesare methylamine, dimethylamine, trimethylamine, ethylamine,diethylamine, triethylamine, propylamine, isopropylamine and butylamine.

The hydroxy amine of group IV(c) may be a primary, secondary or tertiaryamine. It may contain one, two or three hydroxy groups. In a preferredembodiment each hydrocarbyl substituent of the nitrogen is substitutedby not more than one hydroxy group. Preferred amines have up to 20carbon atoms, more preferably between 1 and 10 and especially between 2and 4 carbon atoms as for example between 1 and 20, between 1 and 4,between 2 and 20 or between 2 and 10 carbon atoms. In secondary andtertiary amines the hydrocarbyl respectively hydroxyalkyl residues maybe the same or different. Preferred hydrocarbyl residues are alkyl, aryland alkylaryl residues, with alkyl residues being particularlypreferred. Especially preferred hydroxy amines are hydroxyalkyl amineswith 1 to 4 carbon atoms per alkyl residue. Examples for especiallypreferred hydroxy amines of group IV(c) are monoethanolamine,diethanolamine, 1-amino-2-propanol, 3-amino-1-propanol,2-amino-1-butanol, 3-amino-1-butanol, 3-amino-1-butanol,2-ethoxypropylamine, 3-ethoxypropylamine, 1-methoxyisopropylamine,2-methoxyethylamine, 2-(2-aminoethoxy)ethanol, dimethylethanolamine,N-methyldiethanolamine and monomethylethanolamine.

Preferred multifunctional amines of group IV(d) contain, besides anamino group, at least one further functional group selected from thegroup consisting of amino groups, ether groups and acid groups or anester, amide or salt thereof. Preferred multifunctional amines have upto 50 carbon atoms, more preferably between 1 and 20 and especiallybetween 2 and 10 carbon atoms as for example between 1 and 50, between 1and 10, between 2 and 50 or between 2 and 20 carbon atoms. Thehydrocarbon chains may be linear, branched and/or cyclic. In a preferredembodiment they contain 1 to 10 and especially 2 to 5 as for example 1to 5 further amino groups and/or ether groups. Preferably the amino-and/or ether groups are separated by at least two carbon atoms. Examplesfor especially preferred multifunctional amines of group IV(d) areethylenediamine, diethylenetriamine, triethylenetetramine,tetraethylenepentamine, poly(ethylene imine), propylene diamine,dipropylenetriamine, N,N-dimethyldipropylenetriamine,aminoethylenepiperazine, aminoethylethanolamine, tallow fatty propylenediamine ethoxylated with 2 to 20 moles ethylene oxide, oleyl amineethoxylated with 2 to 20 mole ethylene oxide, morpholine and piperazine.

In a further preferred embodiment the multifunctional amines of groupIV(d) contain, besides an amino group, an acid group or an ester, amideor salt thereof. Preferred acid groups are sulfonic acids, phosphoricacids and carboxylic acids. Especially preferred multifunctional aminescarrying a carboxylic acid group are amino acids. Preferred amino acidsinclude proteinogenic and non-proteinogenic amino acids. The amino groupand the carboxylic acid group may be located at the same or at differentcarbon atoms. Carboxylic acid groups and other acidic groups areespecially preferred in their neutralized form, e.g. as alkaline orearth alkaline salts. Especially preferred amino acids contain furtherfunctional groups including, hydroxyl, carboxyl, amide, ether,guanidino, hydroxyphenyl, imidazolyl and/or further amine groups.Examples of preferred multifunctional amines carrying and acid group areglycine, alanine, leucine, isoleucine, proline, serine, threonine,asparagine, glutamine, phenylalanine, tryptophan, tyrosine, valine,aspartic acid, glutamic acid, methionine, sarcosine and taurine andtheir carboxylate salts with sodium and/or potassium. Especiallypreferred amino acids are glycine, lysine, histidine and arginine.

When mixtures IV(d) of alkaline compounds of the groups IV(a) to IV(c)are used, they may comprise 2 or more, preferably 2 to 10 and especially3 to 5 as for example two, three, four or five different componentsselected form the groups IV(a) to IV(c). The portion of each individualcompound in the mixture of the compounds of groups IV(a) to IV(c) ispreferably between 5 and 95 wt.- %, more preferably between 10 and 90wt.- % and especially between 20 and 80 wt.- % as for example between 5and 90 wt.- %, between 5 and 80 wt.- %, between 10 and 95 wt.- %,between 10 and 80 wt.- %, between 20 and 95 wt.- % or between 20 and 90wt.- %.

Group V

The group V component is optional. This group comprises emulsionbreakers, demulsifiers and/or non-emulsifiers. The purpose of having thecompounds of group V present is to prevent the formation of emulsionsduring the scavenging process and to improve the efficiency of thescavenging process. Often metal sulfides as for example iron sulfide areformed e.g. by corrosion of pipelines and equipment in the presence ofsulfhydryl compounds. Being in the form of fine solids they accumulateat the oil water interface, thereby stabilizing the water present in theoil and generating a stable emulsion which may affect phase separationand accessibility of the sulfhydryl compounds to be scavenged. Thepurpose of the emulsion breaker, demulsifier and/or non-emulsifier is tobreak the oil/water emulsion by creating a preferentially water wetsurface on the metal sulfide and also to modify the surface tension atthe oil/water interface which is stabilized by the metal sulfides to oneallowing coalescence of the emulsion .

In a preferred embodiment, the emulsion breaker of group V is part ofthe inventive composition comprising compounds of groups I and II, ofgroups I, II and III, of groups I, II and IV or of groups I, II, Ill andIV. Preferred emulsion breakers are polymeric nonionic surfactants,including but not limited to polysorbates, polymers comprising ethyleneoxide, polymers comprising propylene oxide, ethylene oxide-propyleneoxide copolymers, alkyl polyglucosides such as decyl maltoside,alkylphenol ethoxylates, and ethoxylated and/or propoxylated alkylphenol-formaldehyde resins. The emulsion breaker can also be a fattyalcohol alkoxylated with 1 to 200 moles, preferably with 2 to 100 molesand especially with 5 to 50 moles as for example with 1 to 100 moles or1 to 50 moles or 2 to 50 moles or with 5 to 100 moles of alkylene oxide.Examples for preferred alkylene oxides are ethylene oxide, propyleneoxide and their mixtures; preferred fatty alcohols have a C₄- toC₃₆-alkyl residue and especially a C₈- to C₂₄-alkyl residue as forexample a C₄- to C₂₄-alkyl residue or a C₈- to C₃₂-alkyl residue such ascetyl alcohol and oleyl alcohol.

In a preferred embodiment, the emulsion breaker is a compound accordingto the formula (8)

wherein

R₁₀ C₂ to C₄ alkylene

R₁₁ C₁ to C₁₈ alkyl

k a number from 1 to 200

m a number from 1 to 100 is.

In a preferred embodiment R₁₀ is an ethylene or a propylene group. R₁₀may represent mixtures of different C₂ to C₄ alkylene groups, preferablyethylene and propylene groups.

In another preferred embodiment, R₁₁ is a C₄ to C₁₂ alkyl group, morepreferably a tertiary butyl group or an iso-nonyl group.

In formula (8), R₁₀, R₁₁ and k may be the same in each of the repeatingunits, or they may differ from unit to unit.

In another preferred embodiment k is a number from 2 to 20.

In another preferred embodiment m is a number from 3 to 20.

In another specific preferred embodiment the emulsion breaker is analkylbenzenesulfonic as for example dodecylbenzesulfonic acid (9) or itssalt with an alkaline metal, ammonia or a primary, secondary or tertiaryamine as for example methylamine, ethylamine, propylamine, diethylamine,dimethylamine, trimethylamine, ethanolamine, diethanolamine ortriethanolamine.

In another preferred embodiment, the demulsifier is a mixture of atleast one compound of formula (8) and an alkylbenzene sulfonic acid (9)or its salt. Such mixture preferably contains (8) and sulfonic acid (9),respectively its salt, in a weight ratio of from 5:1 to 1:5, morepreferably in a weight ratio of from 3:1 to 1:3.

The polymeric nonionic surfactant may be added to the further componentsof the inventive composition neat or preferably dissolved or suspendedin a solvent. Any solvent suitable for dissolving or suspending apolymeric nonionic surfactant may be used. Examples of suitable solventsinclude water, ethylene glycol, propylene glycol, butylene glycol,oligoethylene glycols, oligopropylene glycols, ethers including glycolethers like methoxyethane, dimethoxyethane and butoxyethanol, alcohols,toluene, xylene, aromatic naphtha, or any combination thereof. Thealcohol may include any alcohol suitable for use with oil recovery andfor dissolving the polymeric nonionic surfactant and is preferablyselected from the group consisting of methanol, ethanol, propanol,isopropyl alcohol, butanol, 2-ethyl hexanol or any combination thereof.

Group VI

The group VI component is optional. This group comprises corrosioninhibitors and serves to add corrosion inhibition functionality to theinventive composition. The addition of a corrosion inhibitor may not berequired because the synergist of group III provides sufficientcorrosion inhibition to protect the integrity of the whole asset.

However, often addition of a further corrosion inhibitor is advisable toreduce the overall corrosivity, protecting the tubulars and productionequipment from corrosion caused by oilfield fluids and gases into whichthe instant invention is deployed.

A preferred embodiment of the current invention is to use alkyl dimethylbenzyl ammonium chloride according to formula (10) as a corrosioninhibitor that also provides functionality as an interfacial tensionreducer.

wherein R⁹ is C₈ to C₁₈ alkyl.

The inventive composition may additionally contain biocides, forexample, formaldehyde or glutaraldehyde, water dispersants such aspolyacrylamide based dispersants, oxygen scavengers, antifoams such asacetylenic diols, silicones or polyethoxylated antifoams, and/orflocculants. Preferably their content is less than 10 wt.- % andespecially less than 5 wt.- % relative to the components of the groups Ito VI.

In a preferred embodiment, the inventive composition comprises 1 to 60wt.- % based on its content of active components of groups I to IV ofthe reaction product of the monohydric alcohol described above in groupI, preferably between 5 and 50 wt.- % and especially between 10 and 40wt.- % as for example between 1 and 50 wt.- % or between 1 and 40 wt.- %or between 5 and 60 wt.- % or between 5 and 40 wt.- % or between 10 and60 wt.- % or between 10 and 50 wt.- %.

In a preferred embodiment, the inventive composition comprises 1 to 95wt.- % based on its content of active components of groups I to IV ofthe reaction product of the monosaccharide having 3 to 6 carbon atomsand/or the oligosaccharide being formed by oligomerization ofmonosaccharides having 3 to 6 carbon atoms described above in group II,preferably between 10 and 90 wt.- %, more preferably between 20 and 80wt.- % and especially between 25 and 75 wt.- % as for example between 1and 90 wt.- % or between 1 and 80 wt.- % or 1 and 75 wt.- % or between10 and 95 wt.- % or between 10 and 80 wt.- % or between 10 and 75 wt.- %or between 20 an d95 wt.- % or between 20 and 90 wt.- % or between 20and 75 wt.- % or between 25 and 90 wt.- % or between 25 and 80 wt.- %.

The molar ratio between the reaction product of the monohydric alcoholand an aldehyde or ketone (group I) and the reaction product of themonosaccharide having 3 to 6 carbon atoms and/or the oligosaccharidebeing formed by oligomerization of monosaccharides having 3 to 6 carbonatoms and an aldehyde having one or two carbon atoms (group II) ispreferably between 20:1 and 1:20, preferably between 10:1 and 1:10 andespecially between 5:1 and 1:5 as for example between 20:1 and 1:10,between 20:1 and 1:5, between 10:1 and 1:20, between 10:1 and 1:5,between 5:1 and 1:20 or between 5:1 and 1:10.

In a preferred embodiment, the inventive composition comprises 0.1 to 20wt.- % based on its content of active components of groups I to IV ofthe synergist described above in group III, preferably between 0.5 and15 wt.- % and especially between 1 and 10 wt.- % as for example between0.1 and 15 wt.- % or between 0.1 and 10 wt.- % or between 0.5 and 20wt.- % or between 0.5 and 10 wt.- % or between 1 and 20 wt.- % orbetween 1 and 15 wt.- %.

The weight ratio between the reaction products of group I and group IItogether and the synergist (group III) on the other hand side ispreferably between 1000:1 and 5:1, more preferably between 500:1 and10:1 and especially between 100:1 and 10:1 as for example between 1000:1and 10:1, between 500:1 and 5:1 or between 100:1 and 5:1.

In a preferred embodiment, the inventive composition comprises 0.1 to 15wt.- % based on its content of active components of groups I to IV of atleast one solids suppression agent described above in group IV,preferably between 0.5 and 10 wt.- % and especially between 1 and 8 wt.-%, as for example between 1 and 10 wt.- % or between 1 and 8 wt.- % orbetween 5 and 15 wt.- % or between 5 and 8 wt.- % or between 7 and 15wt.- % or between 7 and 10 wt.- %.

In a preferred embodiment, the inventive composition comprises 0.1 to 10wt.- % based on its content of active components of groups I to VI of atleast one emulsion breaker described above in group V, preferablybetween 0.5 and 5 wt.- %.

In a preferred embodiment, the inventive composition comprises 0.1 to 10wt.- % based on its content of active components of groups I to VI ofthe corrosion inhibitor described above in group VI, preferably between0.2 and 5 wt.- %.

In a preferred embodiment the compounds of groups Ito IV sum up to 100wt.- %. In a further preferred embodiment the compounds of groups I toIV sum up to 100 wt.- %.

The inventive composition is preferably applied to the oil or gas to betreated in amounts of 0.5 to 50 wt.-ppm, more preferably 1 to 30 wt.-ppmand especially 2 to 20 wt.-ppm as for example 0.5 to 30 wt.-ppm, 0.5 to20 wt.-ppm, 1 to 50 wt.-ppm, 1 to 20 wt.-ppm, 2 to 50 wt.-ppm or 2 to 30wt.-ppm per 1 ppm of sulfur contained in the oil or gas.

The use of undiluted compositions according to the invention has provenespecially successful in gas contact towers.

In a preferred embodiment the compositions according to the differentaspects of the invention are used in formulations additionallycomprising water. The water in the formulation may be formed during themanufacture of hemiacetals, or it can be introduced as a solvent for thereactants or it can be added to the composition to balance theformulation. Preferably water is present in a concentration from 1 to 90wt.- %, preferably between 5 and 80 wt.- % as for example between 1 and80 wt.- % or between 5 and 90 wt.- % of the formulation. In anotherpreferred embodiment water is present to balance up to 100 wt.- % of theformulation.

Alternatively, any balance remaining in a formulated compositionaccording to the different aspects of the invention is made up withwater and/or glycol and/or alcohol based solvents in the amounts givenabove for water alone. Preferred alcohols and glycols are selected from,but not limited to, methanol, ethanol, propan-1-ol, propan-2-ol,ethylene glycol, diethylene glycol, triethylene glycol, neopentylglycol, 2-butoxyethanol, glycerol and their mixtures.

The inventive compositions can be made by mixing of the compounds ofgroups I and II, of groups I, II and III, of groups I, II and IVrespectively of groups I, II, II and IV each optionally with compoundsof groups V and/or VI. The sequence of addition of the individualcompounds is not important. In a preferred embodiment the compounds ofgroups I and II are produced simultaneously in a single pot reaction andsubsequently the compounds of groups III and/or IV and optionally Vand/or VI are added. For the production of formulations water and/orother solvents can be added to the inventive composition. Alternatively,some or all of the components to make up the inventive composition maycontain solvent.

A formulated product containing the inventive composition and solvent ispreferably applied in concentrations between 5 and 40,000 mg/L,preferably between 50 and 30,000 mg/L and especially between 100 and25,000 mg/L as for example between 5 and 40,000 mg/L, between 5 and25,000 mg/L, between 50 and 40,000 mg/L, between 50 and 25,000 mg/L,between 100 and 40,000 mg/L and between 100 and 30,000 mg/L based on thevolume of oil or gas production to be treated. The preferred and bestsuited concentration of the formulation depends on the formulationactivity itself, the type and amount of sulfhydryl compounds to bescavenged, static conditions, temperature and salinity of the system.Furthermore, the material grade of the equipment used for operating thescavenging process should be taken into account: If e.g. a contact toweris made of stainless steel a more concentrated product can be appliedwhile it has proven to be advantageous to apply more dilute productformulations, preferably containing a corrosion inhibitor of group VI,if a poor material of construction as for example carbon steel is used.

At the given concentration range, the inventive composition providessubstantial scavenging of sulfhydryl compounds from the treated liquidsand gases and ensures a specified sulfur content of e. g. the producedhydrocarbon as it is brought to the market and therefore its safehandling. Furthermore flowability of the treated hydrocarbon will not beimpaired due to retardation resp. prevention of the formation of solidsulfhydryl reaction products.

The present invention also includes a process for application of theinventive composition in scavenging of sulfhydryl compounds present inthe drilling and the production cycle of mineral oil, particularly as acomponent of well work-over, well intervention, production enhancementand flow assurance packages.

The composition according to the invention may be injected into asulfhydryl compound containing stream together with other ingredientsknown to those familiar with the art. Such other ingredients includeacids, dispersants, viscosifiers, lubricity agents, scale inhibitors,friction reducers, cross linker, surfactants, pH adjuster, iron controlagents, breakers; this is especially advantageous if any produced water(or recycled water) is in contact with the compositions of the instantinvention.

Employing the embodiments of the instant invention allows either i) fora lower dosage rate of scavenger to obtain the same level of residualamount of sulfhydryl compound or ii) for a lower level of residualamount of sulfhydryl compound with the same dosage rate of scavenger incomparison to hemiacetals and/or acetals according to the state of theart. Additionally, in combination with a reaction product fromformaldehyde and an amine the kinetics of scavenging H₂S and/ormercaptans provided by the mixture of hemiacetals and/or acetalscontaining the reaction products of a monohydric alcohol with analdehyde and/or ketone and of a monosaccharide having 3 to 6 carbonatoms and/or an oligosaccharide being formed by oligomerization ofmonosaccharides having 3 to 6 carbon atoms with an aldehyde having oneor two carbons atoms can be significantly accelerated. This allows for amuch more efficient scavenging of sulfhydryl compounds especially inapplications where only short contact times between the oil or gas andthe scavenger are available, as for example in contact towers and directinjection applications for treatment of gases. By admixture of a solidssuppression agent to the mixture of hemiacetals and/or acetalscontaining the reaction products of a monohydric alcohol with analdehyde and/or ketone and of a monosaccharide having 3 to 6 carbonatoms or a disaccharide with an aldehyde having one or two carbons atomsas a further synergistic additive the gas breakthrough time of a systemcontaining sulfhydryl compounds is extended. While improving thescavenging of sulfhydryl compounds no formation of complex and difficultto treat emulsions is observed. Furthermore the embodiments of theinstant invention will not corrode the oilfield equipment that it comesinto contact with, nor will it allow the deposition of unwanted solids,such as polymethylenesulfide oligomers and metal sulfide scales, sooften found with applications of the prior art. Other applications ofthe embodiments of the instantaneous invention include treating waterfor downhole injection for pressure support, treatment of drilling andwork-over operations, wettability alteration and well cleanout.

Within this specification, percentages are weight percentages unlessspecified otherwise.

EXAMPLES

Preparation of Hemiacetals

Method A (using paraformaldehyde, PFA): The amounts of alcohols and/orsugars and water given in table 1 were charged into a stirred reactor.0.25 wt.- % (based on the mass of alcohols) of sodium hydroxide solutionat 50 wt.- % was added. This mixture was homogenized for 10 minutesbefore paraformaldehyde (PFA, 93 wt.- %) was added in the amount givenin table 1 over a period of approximately 30 minutes. The reactionmixture was warmed while stirring for 8 hours at a temperature between80 to 85° C. After the reaction time, the mixture was cooled to 30° C.

Method B (using aqueous formaldehyde, AFA): A stirred reactor wascharged with the quantities of an aqueous solution of formaldehyde (AFA,37 wt.- %) given in table 1 . Then, amounts of alcohols and/or sugarsgiven in table 1 were added followed by 0.25 wt.- % (based on the massof alcohols) of sodium hydroxide solution at 50 wt.- %. This mixture washomogenized for 10 minutes before heating the stirred reaction mixtureto to a temperature between 80 to 85° C. for 8 hours. After the reactiontime, the mixture was cooled to 30° C.

The reaction products are characterized by the molar amounts ofhemiacetal in respect to the total amount of hydroxyl groups charged andthe content of free formaldehyde (CH₂O) as determined by ¹H NMRspectroscopy.

Further materials used were

-   -   hexahydro-1,3,5-trimethyl-s-triazin (HTT) and        3,3′-methylenebis-5-methyloxazolidine (MBO) as the synergists        according to group III.    -   triethylamine (TEA), monoethanolamine (MEA), piperazine (PIP), 5        wt.- % aqueous solution of NaOH (NaOH), and the monosodium salt        of glycine (GLY) as the solids suppressants according to        group IV. All these materials were commercial grades.

TABLE 1 Preparation of (hemi-)acetals reactor charge reaction productmonohydric water formaldehyde acetalized CH₂O (hemi-)acetal alcoholcharge [g] sugar charge [g] [g] source charge [g] [mol-%] [wt.-%] A1(comp.) methanol 500 — 0 0 PFA 500 98% 0.07 A2 (comp.) ethanol 600 — 0 0PFA 420 99% 0.06 A3 (comp.) i-propanol 600 — 0 0 PFA 320 99% 0.08 A4(comp.) 2-EH 800 — 0 0 PFA 200 98% 0.11 A5 (comp.) — 0 glucose 780 0 AFA1036 76 0.07 A6 (comp.) — 0 sucrose 1033 988 PFA 624 71 0.12 A7 (comp.)— 0 xylose 694 0 AFA 1200 73 0.09 A8 methanol 128 glucose 721 982 PFA620 79 0.05 A9 methanol 64 sucrose 685 736 PFA 464 75 0.10 A10 methanol80 xylose 375 511 PFA 323 74 0.06 A11 methanol 96 fructose 772 0 AFA 87758 0.07 A12 methanol 96 lactose 1027 500 PFA 872 95 0.11 A13 ethanol 157lactose 1663 0 AFA 1738 67 0.09 2-EH = 2-ethyl hexanol

Scavenger Performance Tests—Efficiency

In order to demonstrate the improved efficiency of the instant inventionin removing sulfhydryl compounds compared to group I respectively groupII compounds alone, the removal of H₂S from an oil and from an oil/watermixture was measured.

The oil used was a mixture of kerosene with 10% of xylene with zerobottom sediment and water (BS&W) to simulate oil field conditions.

The oil/water mixture was a mixture of the oil described above and brine(in a 50:50 volume ratio of oil to aqueous phase) to mimic theefficiency in hydrated crude oil.

In a 500 mL stirred autoclave (Parr reactor), 350 mL of the oilrespectively the oil/brine mixture was de-aerated for 1 hour with N₂,then saturated with a sour gas mixture of 0.2 wt.- % H₂S and 99.8 wt. %CO₂, by purging this gas into the oil resp.

oil/brine mixture with a flow rate of 0.6 L/min. After equilibration bythe sour gas mixture, 1000 ppm of the composition to be tested wasinjected into the autoclave by an HPLC pump.

For reasons of better comparability of performance tests thecompositions given in tables 2 and 3, containing (hemi-)acetal,synergist and/or solids suppressant as active materials, were applied as50 wt.- % active aqueous formulations. The portions of (hemi-)acetal,synergist and solids suppressant given in tables 2, 3 and 4 refer to theportion of the respective component in the active material, thereforesumming up to 100%. For preparation of the compositions given in tables2, 3 and 4 the water content introduced during preparation of the(hemi-)acetals A1 to A13 according to table 1 was taken into account.

The performance tests were carried out at 30° C. and under 1 bar, usinga gas chromatograph to measure the outlet H₂S content in the gas phaseevery two minutes. Then, a graph of the measured values of H₂S content(ppm) versus time (min) was plotted. The amount of hydrogen sulfidescavenged is the area above the resultant performance curve, which iscalculated by the integration of the curve. For all samples theintegration of the curve was done up to 60 min after the injection ofH₂S-scavenger. As the output parameter of this performance testL_(sc)/kgH₂S (Liters of H₂S scavenger required to remove 1 kg of H₂Sfrom the system) has been determined for 6 minutes and 1 hour ofanalysis. All consumption values (L_(sc)/kgH₂S) refer to the amount of100% active composition consumed in the test and are averages of threerepeat tests. The test results have been summarized in Table 2 and Table3. Percentages mean weight percent if not indicated otherwise. Ratios inmixtures of (hemi-)acetals refer to the mass portions of activematerial.

TABLE 2 Performance tests for H₂S-scavengers in oil (zero BS&W) solids(hemi)acetal synergist suppressant amount amount amount L_(sc)/kg H₂Sexample type [wt %] type [wt %] type [wt %] @ 6 min. @ 1 hour P1 (comp.)A1 100 — 0 — 0 19.45 8.70 P2 (comp.) A2 100 — 0 — 0 20.76 9.56 P3(comp.) A3 100 — 0 — 0 21.23 10.04 P4 (comp.) A5 100 — 0 — 0 19.53 9.43P5 (comp.) A6 100 — 0 — 0 19.10 9.53 P6 (comp.) A1 + A2 100 — 0 — 019.12 9.85 (1:1) P7 (comp.) A5 + A6 100 — 0 — 0 18.87 9.06 (1:1) P8 A1 +A5 100 — 0 — 0 14.56 7.80 (1:1) P9 A1 + A6 100 — 0 — 0 15.18 7.59 (1:2)P10 A2 + A5 100 — 0 — 0 15.21 8.07 (1:3) P11 A8 100 — 0 — 0 13.61 7.01P12 A9 100 — 0 — 0 13.43 6.93 P13 (comp.) A1 98 MBO 2 — 0 5.31 4.22 P14(comp.) A2 98 MBO 2 — 0 5.65 4.63 P15 (comp.) A3 98 MBO 2 — 0 5.86 4.86P16 (comp.) A5 98 MBO 2 — 0 5.52 4.67 P17 (comp.) A6 98 MBO 2 — 0 5.374.49 P18 A1 + A5 98 MBO 2 — 0 3.27 2.94 (1:1) P19 A1 + A6 98 MBO 2 — 03.98 3.00 (1:2) P20 A2 + A6 98 MBO 2 — 0 3.95 2.97 (1:3) P21 A3 + A5 98MBO 2 — 0 4.01 3.06 (1:3) P22 A8 96 HTT 4 — 0 3.40 3.01 P23 A9 96 HTT 4— 0 3.35 2.98 P24 A12 96 HTT 4 — 0 3.16 2.72 P25 (comp.) A1 93 — 0 GLY 73.10 2.70 P26 (comp.) A2 93 — 0 MEA 7 3.23 2.87 P27 (comp.) A5 95 — 0NaOH 5 3.17 2.84 P28 (comp.) A6 93 — 0 PIP 7 3.45 2.93 P29 A1 + A5 93 —0 GLY 7 3.23 2.83 (1:1) P30 A8 93 — 0 GLY 7 3.09 2.90 P31 A8 95 — 0 NaOH5 3.16 2.92 P32 A9 93 — 0 PIP 7 3.25 2.89 P33 A9 93 — 0 MEA 7 3.38 3.04P34 (comp.) A1 93 MBO 2 MEA 5 4.46 3.93 P35 (comp.) A2 90 MBO 2 PIP 84.76 4.06 P36 (comp.) A3 88 MBO 2 TEA 10 4.80 4.12 P37 (comp.) A5 93 MBO2 MEA 5 4.53 3.87 P38 (comp.) A6 90 MBO 2 PIP 8 4.38 3.62 P39 A1 + A5 93MBO 2 MEA 5 2.65 2.36 (1:1) P40 A1 + A6 93 MBO 2 MEA 5 2.30 2.08 (1:2)P41 A2 + A5 88 MBO 2 TEA 10 2.78 2.48 (1:2) P42 A3 + A6 93 MBO 2 MEA 52.89 2.31 (1:3) P43 A8 93 MBO 2 MEA 5 2.38 2.21 P44 A8 89 HTT 4 GLY 72.37 2.09 P46 A8 91 HTT 4 NaOH 5 2.40 2.11 P47 A9 89 HTT 4 PIP 7 2.412.23 P48 A9 89 HTT 4 MEA 7 2.39 2.17 P49 A11 89 HTT 4 GLY 7 2.47 2.19P50 A12 89 HTT 4 GLY 7 2.38 2.10

TABLE 3 Performance tests for H₂S-scavenging in a mixture of the oil andbrine (50:50 volume ratio of oil to aqueous phase) solids (hemi)acetalsynergist suppressant amount amount amount L_(sc)/kg H₂S example type[wt %] type [wt %] type [wt %] @ 6 min. @ 1 hour P51 (comp.) A1 100 — 0— 0 23.36 10.04 P52 (comp.) A2 100 — 0 — 0 23.82 10.20 P53 (comp.) A4100 — 0 — 0 28.51 14.21 P54 (comp.) A5 100 — 0 — 0 22.64 9.84 P55(comp.) A7 100 — 0 — 0 21.84 9.21 P56 (comp.) A1 + A2 100 — 0 — 0 21.879.95 (1:1) P57 A1 + A5 100 — 0 — 0 18.97 7.99 (1:1) P58 A1 + A7 100 — 0— 0 19.14 8.05 (1:3) P59 A4 + A7 100 — 0 — 0 19.46 8.11 (1:1) P60 A2 +A5 100 — 0 — 0 19.21 8.07 (1:1) P61 A8 100 — 0 — 0 18.75 7.94 P62 A10100 — 0 — 0 18.81 7.96 P63 A11 100 — 0 — 0 18.72 8.01 P64 (comp.) A1 94HTT 6 — 0 8.76 7.04 P65 (comp.) A2 98 MBO 2 — 0 8.40 6.88 P66 (comp.) A498 HTT 2 — 0 8.45 7.12 P67 (comp.) A5 98 MBO 2 — 0 8.56 6.96 P68 (comp.)A7 94 HTT 6 — 0 8.63 7.01 P69 A1 + A5 98 MBO 2 — 0 7.95 6.84 (1:1) P70A1 + A7 94 HTT 6 — 0 8.03 6.99 (2:1) P71 A4 + A7 94 HTT 6 — 0 7.86 6.91(1:3) P72 A2 + A5 98 MBO 2 — 0 7.94 6.90 (1:2) P73 A8 94 HTT 6 — 0 7.776.84 P74 A10 98 MBO 2 — 0 7.83 6.72 P75 A10 94 HTT 6 — 0 7.71 6.76 P76(comp.) A1 95 — 0 NaOH 5 7.56 6.66 P77 (comp.) A2 93 — 0 GLY 7 7.62 6.71P78 (comp.) A4 93 — 0 MEA 7 7.70 6.78 P79 (comp.) A5 93 — 0 GLY 7 7.636.70 P80 (comp.) A7 93 — 0 PIP 7 7.68 6.73 P81 A8 93 — 0 GLY 7 7.60 6.69P82 A8 93 — 0 MEA 7 7.61 6.70 P83 A10 93 — 0 GLY 7 7.64 6.63 P84 A10 93— 0 MEA 7 7.62 6.65 P85 A13 90 — 0 TEA 10 7.84 6.82 P86 A2 + A5 90 — 0MEA 10 7.60 6.67 (1:4) P87 A10 90 — 0 MEA 10 7.61 6.65 P88 (comp.) A1 89HTT 6 NaOH 5 6.91 5.72 P89 (comp.) A2 88 MBO 2 MEA 10 6.52 5.56 P90(comp.) A5 88 MBO 2 MEA 10 7.05 5.92 P91 (comp.) A7 89 HTT 6 NaOH 5 7.065.95 P92 A1 + A5 88 MBO 2 MEA 10 6.95 5.62 (1:1) P93 A1 + A7 89 HTT 6NaOH 5 6.97 5.78 (2:1) P94 A4 + A7 89 HTT 6 NaOH 5 7.00 5.94 (1:3) P95A2 + A5 89 HTT 4 GLY 7 6.63 5.60 (1:2) P96 A8 89 HT 6 NaOH 5 6.57 5.59P97 A8 89 HTT 4 GLY 7 6.53 5.54 P98 A8 89 HTT 4 MEA 7 6.55 5.56 P99 A991 HTT 4 NaOH 5 6.71 5.60 P100 A9 89 HTT 4 PIP 7 6.69 5.63 P101 A10 88MBO 2 MEA 10 6.60 5.59 P102 A10 89 HTT 4 GLY 7 6.58 5.53 P103 A10 89 HTT4 PIP 7 6.56 5.50 P104 A12 89 HTT 6 NaOH 5 6.50 5.49 P105 A13 89 HTT 6NaOH 5 6.66 5.67

In tables 2 and 3 the lower consumption of the scavenger to remove 1 kgof H₂S, the more efficient is the scavenger. In the inventive examplesthe mixtures of acetals being based on mixtures of a monohydric alcoholsand a monosaccharide having 3 to 6 carbon atoms and/or anoligosaccharide being formed by oligomerization of monosaccharideshaving 3 to 6 carbon atoms are more efficient than the singlecomponents. The efficiency is further improved by the incorporation of asynergist and/or a solids suppressant. Furthermore, incorporation of thesynergist enhances the reaction rate in the initial phase of the test ascan be seen from the difference between scavenging efficiency after 6minutes versus 1 hour.

Scavenger Performance Tests—Gas Breakthrough

The performance of the H₂S scavengers according to the invention wasevaluated for their ability to remove H₂S from a flowing gas stream bypassing gas laden with H₂S through a column of fluid containing thescavenger chemical. A sour gas mixture of 0.2% H₂S and 99.8% CO₂ waspurged with a flow rate of 60 mL/min through 440 mL of a 22% activesolution of the scavenger composition in water. Under these conditionsthe average contact time of gas and scavenger was about 4 seconds.Initially all of the H₂S is removed from the gas stream and no H₂S isdetected in the effluent gas. At some point in time (the breakthroughtime or TBT) the chemical can no longer entirely remove H₂S from the gasstream and H₂S is observed in the effluent. This parameter is a measureof the efficacy of the scavenger especially for contact towerapplications with short contact time. The longer the break through timethe more efficient is the chemical scavenger.

The effect of the solids suppression agent is rated by visual inspectionof the spent scavenger fluid after the gas breakthrough test. The degreeof solids formation is rated opaque>turbid>opalescent>clear.

The overall concentration of the scavenger formulations in all examplesis 22 wt.- % (active ingredients), i. e. in examples where synergistand/or solids suppressant is present the concentration of (hemi-)acetalsis reduced accordingly.

TABLE 4 Gas breakthrough times for different (hemi-)acetals solids(hemi-)acetal synergist suppressant amount amount amount TBT visualexample type [wt.-%] type [wt-%] type [wt-%] [min] inspection B1 (comp.)A1 100 — 0 — 0 31 opaque B2 (comp.) A2 100 — 0 — 0 29 opaque B3 (comp.)A3 100 — 0 — 0 27 opaque B4 (comp.) A5 100 — 0 — 0 30 opaque B5 (comp.)A6 100 — 0 — 0 31 opaque B6 (comp.) A7 100 — 0 — 0 29 opaque B7 (comp.)A1 + A2 100 — 0 — 0 35 opaque (1:1) B8 (comp.) A5 + A7 100 — 0 — 0 37opaque (1:1) B9 A1 + A5 100 — 0 — 0 38 opaque (1:1) B10 A1 + A7 100 — 0— 0 34 opaque (2:1) B11 A2 + A7 100 — 0 — 0 37 opaque (1:3) B12 A3 + A7100 — 0 — 0 36 opaque (1:2) B13 A8 100 — 0 — 0 45 opaque B14 A9 100 — 0— 0 38 opaque B15 A10 100 — 0 — 0 43 opaque B16 A11 100 — 0 — 0 42opaque B17 A12 100 — 0 — 0 39 opaque B18 A13 100 — 0 — 0 37 opaque B19(comp.) A1 93 MBO 7 — 0 76 turbid B20 (comp.) A2 97 HTT 3 — 0 69 turbidB21 (comp.) A3 95 HTT 5 — 0 68 turbid B22 (comp.) A5 97 HTT 3 — 0 75turbid B23 (comp.) A6 93 MBO 7 — 0 70 turbid B24 (comp.) A7 93 MBO 7 — 073 turbid B25 A1 + A5 97 HTT 3 — 0 78 turbid (1:1) B26 A1 + A6 97 HTT 3— 0 74 turbid (2:1) B27 A2 + A7 95 MBO 5 — 0 79 turbid (1:3) B28 A3 + A595 HTT 5 — 0 76 turbid (1:2) B29 A8 96 HTT 4 — 0 80 turbid B30 A9 96 HTT4 — 0 76 turbid B31 A10 96 HTT 4 — 0 77 turbid B32 A12 97 HTT 3 — 0 78turbid B33 A13 93 MBO 7 — 0 75 turbid B34 (comp.) A1 90 — 0 MEA 10 149opalescent B35 (comp.) A2 85 — 0 PIP 15 146 opalescent B36 (comp.) A3 85— 0 PIP 15 134 opalescent B37 (comp.) A5 85 — 0 PIP 15 140 opalescentB38 (comp.) A5 93 — 0 GLY 7 143 opalescent B39 (comp.) A7 90 — 0 MEA 10142 opalescent B40 A1 + A5 85 — 0 PIP 15 146 opalescent (1:1) B41 A1 +A6 85 — 0 PIP 15 140 opalescent (2:1) B42 A2 + A7 85 — 0 PIP 15 144opalescent (1:3) B43 A3 + A5 85 — 0 PIP 15 145 opalescent (1:2) B42 A893 — 0 GLY 7 149 opalescent B43 A8 93 — 0 MEA 7 147 opalescent B44 A9 95— 0 NaOH 5 145 opalescent B45 A9 93 — 0 TEA 7 143 opalescent B46 A10 93— 0 GLY 7 148 opalescent B47 A10 93 — 0 PIP 7 145 opalescent B38 A11 85— 0 PIP 15 146 opalescent B39 A12 90 — 0 MEA 10 143 opalescent B48(comp.) A1 83 MBO 7 MEA 10 215 clear B49 (comp.) A2 82 HTT 3 PIP 15 200clear B50 (comp.) A3 90 HTT 5 PIP 15 192 clear B51 (comp.) A5 82 HTT 3PIP 15 203 clear B51 (comp.) A6 90 HTT 3 GKY 7 193 clear B52 (comp.) A783 MBO 7 MEA 10 201 clear B53 A1 + A5 82 HTT 3 PIP 15 210 clear (1:1)B54 A1 + A6 82 HTT 3 PIP 15 201 clear (2:1) B58 A2 + A7 80 MBO 5 PIP 15202 clear (1:3) B59 A3 + A5 80 HTT 5 PIP 15 200 clear (1:2) B60 A8 89HTT 4 GLY 7 217 clear B61 A8 89 HTT 4 MEA 7 214 clear B62 A9 89 HTT 4TEA 7 203 clear B63 A9 89 HTT 4 PIP 7 207 clear B64 A10 91 HTT 4 NaOH 5215 clear B56 A11 82 HTT 3 PIP 15 208 clear B57 A12 83 MBO 7 MEA 10 210clear

A comparison of the inventive examples and the comparative examplesshows that mixtures of (hemi-)acetals containing reaction products of amonohydric alcohol and a monosaccharide having 3 to 6 carbon atomsand/or an oligosaccharide being formed by oligomerization ofmonosaccharides having 3 to 6 carbon atoms have a higher TBT than thesingle components or mixtures of components of the same group. Theaddition of a synergist according to group III increases the H₂Sscavenging activity of (hemi-)acetals and especially of mixtures of(hemi-)acetals significantly. The scavenging process becomes faster andmore efficient. The addition of a solids suppressant furthersignificantly improves the performance of the scavenger. Formation ofsolids is mostly inhibited which otherwise hampers the accessibility ofpart of the scavenger and furthermore bears the risk of clogging flowlines for the effluent. The enhancement in scavenging efficiency exceedsthe stoichiometric H₂S scavenging capacity of the added synergistconsiderably.

1. Composition comprising I. at least one reaction product between anitrogen-free monohydric alcohol and an aldehyde or ketone, and II. atleast one reaction product between a monosaccharide having 3 to 6 carbonatoms and/or an oligosaccharide being formed by oligomerization ofmonosaccharides having 3 to 6 carbon atoms and an aldehyde or ketonehaving one or two carbon atoms.
 2. Composition according to claim 1,further comprising III. at least one reaction product from formaldehydeand ammonia and/or an amine, selected from the group consisting ofprimary alkyl amines having 1 to 10 carbon atoms, and primary hydroxyalkyl amines having 2 to 10 carbon atoms.
 3. Composition according toclaim 1, further comprising IV. at least one inorganic or organicalkaline compound that functions as a solids suppression agent. 4.Composition according to claim 1, wherein the reaction products I. andII. are hemiacetals and/or acetals.
 5. The composition according toclaim 1, wherein the aldehyde or ketone for the reaction with themonohydric alcohol (I) contains 1 to 10 carbon atoms, preferably 1 to 4carbon atoms.
 6. The composition according to claim 1, wherein thealdehyde or ketone for the reaction with the monohydric alcohol (I) isselected from the group consisting of formaldehyde, paraformaldehyde,glyoxal, acetaldehyde, propionaldehyde, butyraldehyde andglutaraldehyde.
 7. The composition according to claim 1, wherein thealdehyde for the reaction with the monosaccharide having 3 to 6 carbonatoms and/or the oligosaccharide being formed by oligomerization ofmonosaccharides having 3 to 6 carbon atoms (group II) is selected fromthe group consisting of formaldehyde, paraformaldehyde, acetaldehyde andglyoxal.
 8. The composition according to claim 1, wherein the aldehydeor ketone for both components (group I) and (group II) is formaldehyde.9. The composition according to claim 1, wherein the monohydric alcoholcomprises 1 to 15 carbon atoms, preferably 1 to 5 carbon atoms.
 10. Thecomposition according to claim 1, wherein the monohydric alcohol is analiphatic alcohol.
 11. The composition according to claim 1, wherein themonohydric alcohol is selected from the group consisting of methanol,ethanol, propanol, iso-propanol, n-butanol, iso-butanol, tert-butanol,pentanol, hexanol, heptanol and octanol, and any mixture thereof. 12.The composition according to claim 1, wherein the monosaccharide having3 to 6 carbon atoms and/or the oligosaccharide being formed byoligomerization of monosaccharides having 3 to 6 carbon atoms is amonosaccharide having 3 to 6 carbon atoms.
 13. The composition accordingto claim 1, wherein the monosaccharide is a linear polyhydroxycarbonylcompound having the general formula (1)C_(n)(H₂O)_(n)   (1) wherein n is an integer between 3 and
 6. 14. Thecomposition according to claim 13 wherein n is between 4 and
 6. 15. Thecomposition according to claim 14 wherein n is 5 or
 6. 16. Thecomposition according to claim 1, wherein the monosaccharide is apolyhydroxyaldehyde of formula (2)CHO—(CH—OH)_(m)—CH₂OH   (2) wherein m is 1,2,3 or
 4. 17. The compositionaccording to claim 1, wherein the monosaccharide is a polyhydroxyketoneof formula (3)HO—CH₂—C(═O)—(CH—OH)_(p)—CH₂OH   (3) wherein p is 0, 1, 2 or
 3. 18. Thecomposition according to claim 16, wherein the monosaccharide is amixture of open-chain and cyclic form of the polyhydroxyaldehyde offormula (2) respectively the polyhydroxyketone according to formula (3).19. The composition according to claim 1, wherein the monosaccharide isselected from the group consisting of glucose, mannose, galactose,ribose, arabinose, xylose and fructose.
 20. The composition according toclaim 1, wherein the monosaccharide having 3 to 6 carbon atoms and/orthe oligosaccharide being formed by oligomerization of monosaccharideshaving 3 to 6 carbon atoms is an oligosaccharide being formed byoligomerization of monosaccharides having 3 to 6 carbon atoms.
 21. Thecomposition according to claim 1, wherein the oligosaccharide beingformed by oligomerization of monosaccharides having 3 to 6 carbon atomsis a disaccharide being formed by dimerization of monosaccharides having3 to 6 carbon atoms.
 22. The composition according to claim 21 whereinthe disaccharide formed by oligomerization of monosaccharides having 3to 6 carbon atoms has the general formula (4)C_(y)(H₂O)_(y-1)   (4) wherein y is 10, 11 or
 12. 23. The compositionaccording to claim 21 wherein the disaccharide is formed from aldosesand/or ketoses having 5 or 6 carbon atoms which are linked by aglycosidic linkage.
 24. The composition according to claim 20, whereinthe oligosaccharide being formed by oligomerization of monosaccharideshaving 3 to 6 carbon atoms is selected from maltose, Isomaltose,cellobiose, trehalose, sucrose, isomaltulose, trehalulose, lactose,lactulose and raffinose.
 25. The composition according to claim 2,wherein the reaction product III of an amine and formaldehydecorresponds to formula (7a)

wherein R is H or methyl, and n is 1 or
 2. 26. The composition accordingto claim 2, wherein the reaction product III of an amine andformaldehyde corresponds to the formula (7b)

wherein each R¹ is C₁ to C₄ alkyl or C₂ to C₄ hydroxy alkyl.
 27. Thecomposition according to claim 25, wherein the compound of formula 7a is3,3′-methylenebis-5-methyl-oxazolidine.
 28. The composition according toclaim 2, wherein the reaction product III of an amine and formaldehydeis present in the composition in an amount from 1 wt.- % to 20 wt.- %,preferably between 5 wt.- % and 15 wt.- %.
 29. Composition according toclaim 3, wherein the alkaline compound IV. is selected from the groupconsisting of IV(a). alkaline metal salts or alkaline earth metal saltsIV(b). ammonia; alkyl amines, aryl amines or alkylaryl amines IV(c).hydroxy alkyl amines, hydroxy aryl amines or hydroxy alkylaryl aminesIV(d). multifunctional amines containing besides an amino group, atleast one further functional group selected from the group consisting ofamino groups, ether groups and acid groups or an ester, amide or saltthereof IV(e). mixtures of compounds of groups IV(a) to IV(c), wherein“alkyl” means C₁ to C₂₀ alkyl, “aryl” means C₆ to C₂₀ aryl and“alkylaryl” means C₇ to C₂₀ alkylaryl.
 30. Composition according toclaim 1, comprising 1 to 60 wt.- % of the reaction product between amonohydric alcohol and an aldehyde or ketone, preferably between 5 and50 wt.- %.
 31. Composition according to claim 1, comprising 1 to 95 wt.-% of the reaction product between a monosaccharide having 3 to 6 carbonatoms and/or an oligosaccharide being formed by oligomerization ofmonosaccharides having 3 to 6 carbon atoms and an aldehyde or ketone,preferably between 20 and 75 wt.- %.
 32. Composition according to claim1, wherein the molar ratio between the reaction product between amonohydric alcohol and an aldehyde or ketone (group I) and the reactionproduct between a monosaccharide having 3 to 6 carbon atoms and/or anoligosaccharide being formed by oligomerization of monosaccharideshaving 3 to 6 carbon atoms and an aldehyde having one or two carbonatoms (group II) is between 20:1 and 1:20, more preferably between 5:1and 1:5.
 33. Composition according to claim 2, wherein the weight ratiobetween the combined reaction products of groups I and group II on theone hand side and the synergist (group III) on the other hand side isbetween 1000:1 and 5:1.
 34. Composition according to claim 3, comprising0.1 to 15 wt.- %, preferably 0.5 to 10 wt.- % of at least one solidssuppression agent (group IV).
 35. The composition according to one claim1, further comprising an alkyl dimethyl benzyl ammonium chlorideaccording to formula (10) in an amount between 0,01 and 5 wt.- %,preferably between 0,5 and 2 wt.- %

wherein R⁹ is C₈ to C₁₈ alkyl.
 36. The composition according to claim 1,further comprising a demulsifier in an amount between 0.1 to 10 wt.- %,preferably between 0.5 and 2 wt.- %.
 37. The composition according toclaim 36, wherein the demulsifier is selected from the group consistingof polysorbates, fatty alcohols, polymers comprising ethylene oxide,polymers comprising propylene oxide, ethylene oxide-propylene oxidecopolymers, alkyl polyglucosides, alkylphenol ethoxylates, alkylpolyethylene oxide, alkylbenzenesulfonic acid and ethoxylated and/orpropoxylated alkyl phenol-formaldehyde resins.
 38. The compositionaccording to claim 36, wherein the demulsifier corresponds to theformula (8)

wherein R₁₀ is C₂ to C₄ alkylene, R₁₁ is C₁ to C₁₈ alkyl, k is a numberfrom 1 to 200, m is a number from 1 to
 100. 39. Composition according toclaim 36, wherein the demulsifier is dodecylbenezesulfonic acid (9)


40. Composition according to claim 36, wherein the demulsifier is amixture of at least one compound of formula (8) and at least onecompound of formula (9) in a weight ratio of from 5:1 to 1:5, preferablyin a weight ratio of from 3:1 to 1:3.
 41. Formulation, comprising 10 to99 wt.- % of a composition according to claim 1, and 1 to 90 wt.- % of asolvent selected from the group consisting of water, methanol, ethanol,propan-1-ol, propan-2-ol, ethylene glycol, diethylene glycol,triethylene glycol, neopentyl glycol, 2-butoxyethanol, glycerol andtheir mixtures, most preferably water.
 42. Use of a composition orformulation according to claim 1 for scavenging hydrogen sulphide and/ormercaptans.
 43. Use according to claim 42, wherein the scavenging occursfrom fluids or gases produced from subterranean formations.
 44. Useaccording to claim 42, wherein the scavenging from gas is conducted in acontact tower or by direct injection into the gas.
 45. Process for thescavenging of hydrogen sulphide and/or mercaptans, comprising adding toa medium comprising such hydrogen sulphide or mercaptans a compositionor formulation according to claim
 1. 46. Use of a reaction product fromformaldehyde, and ammonia and/or an amine, selected from the groupconsisting of primary alkyl amines having 1 to 10 carbon atoms, andprimary hydroxy alkyl amines having 2 to 10 carbon atoms, as a synergistin the reaction between hydrogen sulphide and/or mercaptans and acomposition comprising I. at least one reaction product between anitrogen-free monohydric alcohol and an aldehyde or ketone, and II. atleast one reaction product between a monosaccharide having 3 to 6 carbonatoms and/or an oligosaccharide being formed by oligomerization ofmonosaccharides having 3 to 6 carbon atoms and an aldehyde or ketone.47. Use of an alkaline compound selected from the group consisting ofIV(a). alkaline metal salts or alkaline earth metal salts IV(b).ammonia; alkyl amines, aryl amines or alkylaryl amines IV(c). hydroxyalkyl amines, hydroxy aryl amines or hydroxy alkylaryl amines IV(d).multifunctional amines containing besides an amino group, at least onefurther functional group selected from the group consisting of aminogroups, ether groups and acid groups or an ester, amide or salt thereofIV(e). mixtures of compounds of groups IV(a) to IV(c) as a synergist inthe reaction between between hydrogen sulphide and/or mercaptans and acomposition comprising I. at least one reaction product between anitrogen-free monohydric alcohol and an aldehyde or ketone, and II. atleast one reaction product between a monosaccharide having 3 to 6 carbonatoms and/or an oligosaccharide being formed by oligomerization ofmonosaccharides having 3 to 6 carbon atoms and an aldehyde or ketone.